//////////////////////////////////////////////////////////////////////////////////////////////////////
// use core::fmt::{Write, Result, Arguments};                                                       //
// use lazy_static::lazy_static;                                                                    //
// use spin::Mutex;                                                                                 //
// use volatile::Volatile;                                                                          //
//                                                                                                  //
// #[allow(dead_code)]                                                                              //
// #[derive(Debug, Clone, Copy, PartialEq, Eq)]                                                     //
// #[repr(u8)]                                                                                      //
// pub enum Color {                                                                                 //
//     Black = 0,                                                                                   //
//     Blue = 1,                                                                                    //
//     Green = 2,                                                                                   //
//     Cyan = 3,                                                                                    //
//     Red = 4,                                                                                     //
//     Magenta = 5,                                                                                 //
//     Brown = 6,                                                                                   //
//     LightGray = 7,                                                                               //
//     DarkGray = 8,                                                                                //
//     LightBlue = 9,                                                                               //
//     LightGreen = 10,                                                                             //
//     LightCyan = 11,                                                                              //
//     LightRed = 12,                                                                               //
//     Pink = 13,                                                                                   //
//     Yellow = 14,                                                                                 //
//     White = 15,                                                                                  //
// }                                                                                                //
//                                                                                                  //
// #[derive(Debug, Copy, Clone, PartialEq, Eq)]                                                     //
// #[repr(transparent)]                                                                             //
// struct ColorCode(u8);                                                                            //
//                                                                                                  //
// impl ColorCode {                                                                                 //
//     fn new(forground: Color, background: Color) -> ColorCode {                                   //
//         ColorCode((background as u8) << 4 | (forground as u8))                                   //
//     }                                                                                            //
// }                                                                                                //
//                                                                                                  //
// #[derive(Debug, Clone, Copy, PartialEq, Eq)]                                                     //
// #[repr(C)]                                                                                       //
// struct ScreenChar {                                                                              //
//     ascii_character: u8,                                                                         //
//     color_code: ColorCode,                                                                       //
// }                                                                                                //
//                                                                                                  //
// const BUFFER_WIDTH: usize = 80; // NOTE: change here can move the position of text that print to //
//                                 // screen                                                        //
// const BUFFER_HEIGHT: usize = 25;                                                                 //
//                                                                                                  //
// #[repr(transparent)]                                                                             //
// struct Buffer {                                                                                  //
//     chars: [[Volatile<ScreenChar>; BUFFER_WIDTH]; BUFFER_HEIGHT],                                //
// }                                                                                                //
//                                                                                                  //
//                                                                                                  //
// pub struct Writer {                                                                              //
//     column_position: usize,                                                                      //
//     color_code: ColorCode,                                                                       //
//     buffer: &'static mut Buffer,                                                                 //
// }                                                                                                //
//                                                                                                  //
// lazy_static!{                                                                                    //
//     pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer {                                   //
//         column_position: 0,                                                                      //
//         color_code: ColorCode::new(Color::Cyan, Color::Yellow),                                  //
//         buffer: unsafe {&mut *(0xb8000 as *mut Buffer)},                                         //
//     });                                                                                          //
// }                                                                                                //
//                                                                                                  //
// impl Writer {                                                                                    //
//     pub fn write_byte(&mut self, byte: u8) {                                                     //
//         match byte {                                                                             //
//             b'\n' => self.new_line(),                                                            //
//             byte => {                                                                            //
//                 if self.column_position >= BUFFER_WIDTH {                                        //
//                     self.new_line();                                                             //
//                 }                                                                                //
//                                                                                                  //
//                 let row = BUFFER_HEIGHT - 1;                                                     //
//                 let col = self.column_position;                                                  //
//                                                                                                  //
//                 let color_code = self.color_code;                                                //
//                 self.buffer.chars[row][col].write(ScreenChar {                                   //
//                     ascii_character: byte,                                                       //
//                     color_code,                                                                  //
//                 });                                                                              //
//                                                                                                  //
//                 self.column_position += 1;                                                       //
//             }                                                                                    //
//         }                                                                                        //
//     }                                                                                            //
//                                                                                                  //
//     fn write_string(&mut self, s: &str) {                                                        //
//         for byte in s.bytes() {                                                                  //
//             match byte {                                                                         //
//                 0x20..=0x7e | b'\n' => self.write_byte(byte),                                    //
//                 _ => self.write_byte(0xfe),                                                      //
//             }                                                                                    //
//         }                                                                                        //
//     }                                                                                            //
//                                                                                                  //
//     fn new_line(&mut self) {                                                                     //
//                                                                                                  //
//         for row in 1..BUFFER_WIDTH {                                                             //
//             for col in 0..BUFFER_HEIGHT {                                                        //
//                 let character = self.buffer.chars[row][col].read();                              //
//                 self.buffer.chars[row - 1][col].write(character);                                //
//             }                                                                                    //
//         }                                                                                        //
//         self.clear_row(BUFFER_HEIGHT - 1);                                                       //
//         self.column_position = 0;                                                                //
//     }                                                                                            //
//                                                                                                  //
//     fn clear_row(&mut self, row: usize) {                                                        //
//         let blank = ScreenChar {                                                                 //
//             ascii_character: b' ',                                                               //
//             color_code: self.color_code,                                                         //
//         };                                                                                       //
//                                                                                                  //
//         for col in 0..BUFFER_WIDTH {                                                             //
//             self.buffer.chars[row][col].write(blank);                                            //
//         }                                                                                        //
//     }                                                                                            //
// }                                                                                                //
//                                                                                                  //
// impl Write for Writer {                                                                          //
//     fn write_str(&mut self, s: &str) -> Result {                                                 //
//         self.write_string(s);                                                                    //
//         Ok(())                                                                                   //
//     }                                                                                            //
// }                                                                                                //
//                                                                                                  //
//                                                                                                  //
//                                                                                                  //
// // STAGE2                                                                                        //
// // pub fn print_something() {                                                                    //
// //     // STAGE2:                                                                                //
// //     let mut writer = Writer {                                                                 //
// //         column_position: 0,                                                                   //
// //         // NOTE: you can change the color here                                                //
// //         color_code: ColorCode::new(Color::Cyan, Color::Black),                                //
// //         buffer: unsafe {&mut *(0xb8000 as *mut Buffer)},                                      //
// //     };                                                                                        //
// //     // END STAGE2                                                                             //
// //                                                                                               //
// //                                                                                               //
// //     writer.write_byte(b'H');                                                                  //
// //     writer.write_string("ello ");                                                             //
// //     writer.write_string("World!");                                                            //
// //     write!(writer, " The BLOG OS release numbers is {}.{}", 1, 1.0/3.0).unwrap();             //
// // }                                                                                             //
// // END STAGE2                                                                                    //
//                                                                                                  //
// // ---------------------------------------------------                                           //
// #[macro_export]                                                                                  //
// macro_rules! print {                                                                             //
//     ($($arg:tt)*) => ($crate::vga_buffer::_print(format_args!($($arg)*)));                       //
// }                                                                                                //
//                                                                                                  //
// #[macro_export]                                                                                  //
// macro_rules! println {                                                                           //
//     () => ($crate::print!("\n"));                                                                //
//     ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));                           //
// }                                                                                                //
//                                                                                                  //
// #[doc(hidden)]                                                                                   //
// pub fn _print(args: Arguments) {                                                                 //
//     WRITER.lock().write_fmt(args).unwrap();                                                      //
// }                                                                                                //
//////////////////////////////////////////////////////////////////////////////////////////////////////
use core::fmt;
use lazy_static::lazy_static;
use spin::Mutex;
use volatile::Volatile;

lazy_static! {
    /// A global `Writer` instance that can be used for printing to the VGA text buffer.
    ///
    /// Used by the `print!` and `println!` macros.
    pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer {
        column_position: 0,
        color_code: ColorCode::new(Color::Yellow, Color::Black),
        buffer: unsafe { &mut *(0xb8000 as *mut Buffer) },
    });
}

/// The standard color palette in VGA text mode.
#[allow(dead_code)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum Color {
    Black = 0,
    Blue = 1,
    Green = 2,
    Cyan = 3,
    Red = 4,
    Magenta = 5,
    Brown = 6,
    LightGray = 7,
    DarkGray = 8,
    LightBlue = 9,
    LightGreen = 10,
    LightCyan = 11,
    LightRed = 12,
    Pink = 13,
    Yellow = 14,
    White = 15,
}

/// A combination of a foreground and a background color.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(transparent)]
struct ColorCode(u8);

impl ColorCode {
    /// Create a new `ColorCode` with the given foreground and background colors.
    fn new(foreground: Color, background: Color) -> ColorCode {
        ColorCode((background as u8) << 4 | (foreground as u8))
    }
}

/// A screen character in the VGA text buffer, consisting of an ASCII character and a `ColorCode`.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(C)]
struct ScreenChar {
    ascii_character: u8,
    color_code: ColorCode,
}

/// The height of the text buffer (normally 25 lines).
const BUFFER_HEIGHT: usize = 25;
/// The width of the text buffer (normally 80 columns).
const BUFFER_WIDTH: usize = 80;

/// A structure representing the VGA text buffer.
#[repr(transparent)]
struct Buffer {
    chars: [[Volatile<ScreenChar>; BUFFER_WIDTH]; BUFFER_HEIGHT],
}

/// A writer type that allows writing ASCII bytes and strings to an underlying `Buffer`.
///
/// Wraps lines at `BUFFER_WIDTH`. Supports newline characters and implements the
/// `core::fmt::Write` trait.
pub struct Writer {
    column_position: usize,
    color_code: ColorCode,
    buffer: &'static mut Buffer,
}

impl Writer {
    /// Writes an ASCII byte to the buffer.
    ///
    /// Wraps lines at `BUFFER_WIDTH`. Supports the `\n` newline character.
    pub fn write_byte(&mut self, byte: u8) {
        match byte {
            b'\n' => self.new_line(),
            byte => {
                if self.column_position >= BUFFER_WIDTH {
                    self.new_line();
                }

                let row = BUFFER_HEIGHT - 1;
                let col = self.column_position;

                let color_code = self.color_code;
                self.buffer.chars[row][col].write(ScreenChar {
                    ascii_character: byte,
                    color_code,
                });
                self.column_position += 1;
            }
        }
    }

    /// Writes the given ASCII string to the buffer.
    ///
    /// Wraps lines at `BUFFER_WIDTH`. Supports the `\n` newline character. Does **not**
    /// support strings with non-ASCII characters, since they can't be printed in the VGA text
    /// mode.
    fn write_string(&mut self, s: &str) {
        for byte in s.bytes() {
            match byte {
                // printable ASCII byte or newline
                0x20..=0x7e | b'\n' => self.write_byte(byte),
                // not part of printable ASCII range
                _ => self.write_byte(0xfe),
            }
        }
    }

    /// Shifts all lines one line up and clears the last row.
    fn new_line(&mut self) {
        for row in 1..BUFFER_HEIGHT {
            for col in 0..BUFFER_WIDTH {
                let character = self.buffer.chars[row][col].read();
                self.buffer.chars[row - 1][col].write(character);
            }
        }
        self.clear_row(BUFFER_HEIGHT - 1);
        self.column_position = 0;
    }

    /// Clears a row by overwriting it with blank characters.
    fn clear_row(&mut self, row: usize) {
        let blank = ScreenChar {
            ascii_character: b' ',
            color_code: self.color_code,
        };
        for col in 0..BUFFER_WIDTH {
            self.buffer.chars[row][col].write(blank);
        }
    }
}

impl fmt::Write for Writer {
    fn write_str(&mut self, s: &str) -> fmt::Result {
        self.write_string(s);
        Ok(())
    }
}

/// Like the `print!` macro in the standard library, but prints to the VGA text buffer.
#[macro_export]
macro_rules! print {
    ($($arg:tt)*) => ($crate::vga_buffer::_print(format_args!($($arg)*)));
}

/// Like the `println!` macro in the standard library, but prints to the VGA text buffer.
#[macro_export]
macro_rules! println {
    () => ($crate::print!("\n"));
    ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
}

/// Prints the given formatted string to the VGA text buffer through the global `WRITER` instance.
#[doc(hidden)]
pub fn _print(args: fmt::Arguments) {
    use core::fmt::Write;
    WRITER.lock().write_fmt(args).unwrap();
}
